The present invention relates to an improved head suspension having a compliant feature and associated tooling, for efficiently and accurately locating components during assembly of the head suspension.
In a dynamic storage device, a rotating disk is employed to store information in small magnetized domains strategically located on the disk surface. The disk is attached to and rotated by a spindle motor mounted to a frame of the disk storage device. A xe2x80x9chead sliderxe2x80x9d (also commonly referred to simply as a xe2x80x9csliderxe2x80x9d) having a magnetic read/write head is positioned in close proximity to the rotating disk to enable the writing and reading of data to and from the magnetic domains on the disk. The head slider is supported and properly oriented in relationship to the disk by a head suspension that provides forces and compliances necessary for proper slider operation. As the disk in the storage device rotates beneath the slider and head suspension, the air above the disk similarly rotates, thus creating an air bearing which acts with an aerodynamic design of the head slider to create a lift force on the head slider. The lift force is counteracted by the head suspension, thus positioning the slider at a height and alignment above the disk which is referred to as the xe2x80x9cfly height.xe2x80x9d
Typical head suspensions include a load beam, a flexure, and a base plate. The load beam normally includes a mounting region at a proximal end of the load beam for mounting the head suspension to an actuator of the disk drive, a rigid region, and a spring region between the mounting region and the rigid region for providing a spring force to counteract the aerodynamic lift force acting on the slider described above. The base plate is mounted to the mounting region of the load beam to facilitate the attachment of the head suspension to the actuator. The flexure is positioned at the distal end of the load beam, and typically includes a gimbal region having a slider mounting surface to which the slider is mounted and thereby supported in read/write orientation with respect to the rotating disk. The gimbal region is resiliently moveable with respect to the remainder of the flexure in response to the aerodynamic forces generated by the air bearing.
In one type of three-piece head suspension, the flexure is formed as a separate component and further includes a load beam mounting region that is rigidly mounted at the distal end of the load beam using conventional means, such as spot welds. In such a flexure, the gimbal region extends distally from the load beam mounting region of the flexure and includes a cantilever beam to which the slider is mounted. An often spherical dimple that extends between the load beam and the slider mounting surface of the flexure is formed in either the load beam or the slider mounting surface of the flexure. The dimple transfers the spring force generated by the spring region of the load beam to the flexure and the slider to counteract the aerodynamic force generated by the air bearing between the slider and the rotating disk. In this manner, the dimple acts as a xe2x80x9cload pointxe2x80x9d between the flexure/slider and the load beam. The load point dimple also provides clearance between the cantilever beam of the flexure and the load beam, and serves as a point about which the slider can gimbal in pitch and roll directions in response to fluctuations in the aerodynamic forces generated by the air bearing.
Electrical interconnection between the head slider and circuitry in the disk storage device is provided along the length of the head suspension. Conventionally, conductive wires encapsulated in insulating tubes are strung along the length of the head suspension between the head slider and the storage device circuitry. Alternatively, an integrated lead head suspension, such as that described in commonly assigned U.S. Pat. No. 5,491,597 to Bennin et al., that includes one or more conductive traces bonded to the load beam with a dielectric adhesive can be used to provide electrical interconnection. Such an integrated lead head suspension may include one or more bonding pads at the distal end of the traces to which the head slider is attached and that provide electrical interconnection to termiinals on the head slider. The conductive trace can also be configured to provide sufficient resiliency to allow the head slider to gimbal in response to the variations in the aerodynamic forces.
As the number and density of magnetic domains on the rotating disk increase, it becomes increasingly important that the head slider be precisely aligned over the disk to ensure the proper writing and reading of data to and from the magnetic domains. Moreover, misalignments between the head slider and the disk could result in the head slider xe2x80x9ccrashingxe2x80x9d into the disk surface as the slider gimbals due to the close proximity of the head slider to the rotating disk at the slider fly height.
The angular position of the head suspension and the head slider, also known as the static attitude, is calibrated so that when the disk drive is in operation the head slider assumes an optimal orientation at the fly height. It is therefore important that the static attitude of the head suspension be properly established. Toward this end, the flexure must be mounted to the load beam so that misalignments between the flexure and the load beam are minimized since misalignments between the load beam and flexure may introduce a bias in the static attitude of the head suspension and the head slider. It is also important that the load point dimple be properly formed on the head suspension so that it is properly positioned in relation to the head slider when the head slider is mounted to the head suspension. Misalignments between the load point dimple and the head slider may cause a torque to be exerted on the head slider, and thus affect the fly height of the head slider and the orientation of the head slider at the fly height. These concerns are emphasized when integrated leads are used to provide electrical interconnection since the bond pads of the integrated leads (to which the head slider is bonded) are directly affected by the positioning of the flexure.
To assist in the alignment of the head suspension components and in the formation of head suspension features, the head suspension typically includes reference apertures that are engaged by an alignment tool. The apertures are longitudinally spaced apart and are formed in the rigid region of the load beam. In head suspensions that include a separate flexure mounted to the load beam, the flexure includes corresponding apertures formed in the load beam mounting region of the flexure. The reference apertures in the load beam and the flexure are typically circular, and are sized and positioned so as to be substantially concentric when the flexure is mounted to the load beam. In an approach illustrated in U.S. Pat. No. 5,570,249 to Aoyagi et al., rather than being circular, a distal aperture in the load beam is elongated and generally elliptical. The aperture includes a xe2x80x9cvxe2x80x9d shaped portion at one end.
Rigid cylindrical pins on an alignment tool are used to align the individual head suspension components. The rigid pins are spaced apart an amount equal to the longitudinal spacing between the reference apertures in the components. The pins are inserted into and engage the apertures in the load beam and flexure, and in this manner concentrically align the apertures, and thus the load beam and the flexure, to one another. The components can then be fastened together, as by welding or other known processes.
There are certain deficiencies and shortcomings associated with prior art head suspensions, however. Conventional reference apertures such as those described above include manufacturing tolerances that affect the interface between the alignment tool and the head suspension component. The pins on the alignment tools also include manufacturing and positioning tolerances. These tolerances are cumulative so as to affect the alignment of individual head suspension components, and affect the forming of head suspension features, such as a load point dimple. In addition, when aligning individual head suspension components, the manufacturing tolerances in the apertures of the load beam and the flexure are xe2x80x9cstackedxe2x80x9d together because the head suspension components are engaged by common alignment pins, thus creating additional alignment problems. An additional shortcoming is that the alignment pins must typically be manufactured somewhat undersized so as to still be useable when the flexure and load beam apertures overlap each other to create a smaller through-hole for the pins to be inserted in due to manufacturing tolerances and misalignments in the head suspension components. Moreover, because the pins of the alignment tool are spaced apart a fixed distance, the pins may not be able to engage the reference apertures due to the manufacturing tolerances in the apertures.
One head suspension having aligning features that overcome the shortcomings of the described prior art, as well as a method and apparatus for forming such head suspension, is described in commonly assigned U.S. patent application No. 09/003,605 to Heeren et al. This head suspension includes a load beam and a flexure wherein the load beam has a first load beam aperture formed in the load region of the load beam. The flexure comprises a gimbal region and a load beam mounting region, and is mounted at a distal end of the load beam. The flexure has a first flexure aperture formed in the load beam mounting region that is adjacent and coincident with the first load beam aperture when the flexure is aligned over the load beam. An elongated alignment aperture is formed in one of the load beam and the flexure, and a proximal alignment aperture and distal alignment aperture are formed in the other of the load beam and the flexure. The elongated aperture overlaps at least a portion of each of the proximal alignment aperture and the distal alignment aperture so that the proximal perimeter edge of the elongated alignment aperture encroaches upon the proximal alignment aperture and the proximal perimeter edge of the distal alignment aperture encroaches upon the elongated alignment aperture. This configuration of apertures allows the flexure and load beam to be independently aligned relative to each other by dual moving pins of an alignment tool that engage the proximal perimeter edge of the distal alignment aperture and the proximal perimeter edge of the elongated alignment aperture.
An ongoing need exists, however, for improved head suspension designs for use in dynamic storage devices and for supporting head sliders over disk surfaces wherein features are formed in the head suspensions that assist in the efficient and accurate alignment of the head suspension components. Such need is felt in the areas of part manufacturability, cost savings, tool construction, and other tool and alignment related areas.
The present invention meets the ongoing need for improved head suspension designs by providing a head suspension for supporting a head slider over a rigid disk in a dynamic storage device. The head suspension includes compliant features formed in one or more components of the head suspension for use in accurately locating the components relative to tooling or to one another. Such compliant features may also be used for accurately locating other types of small precision components.
The head suspension has a component that includes a compliant feature adapted to be engaged and deflected by a first pin. The component may also include a datum engaging surface spaced from the compliant feature that is adapted to be engaged and positioned relative to a datum. The component is locatable relative to the datum by manipulation of the component with respect to the datum and the first pin. The manipulation causes the first pin to engage and deflect the compliant feature when the datum engaging surface of the component is engaged and positioned with respect to the datum. The compliant feature may be formed in a detachable portion of the head suspension component, which is later detached during head suspension formation. The compliant feature may be formed as a compliant aperture, and the datum engaging surface may be formed as a second aperture with a second pin forming the datum.
The head suspension also may include a second component having a pin engaging feature alignable with the compliant feature of the first component, such that the first pin engages the pin engaging feature and engages and deflects the compliant feature during manipulation. The second component may also include a datum engaging surface alignable with the datum engaging surface of the first component, such that both the datum engaging surfaces are engaged and positioned with respect to the datum during manipulation. The pin engaging feature of the second component may also be a compliant feature. The compliant feature, pin engaging feature and datum engaging surfaces are usable for locating the head suspension components, such as load beams, flexures, and base plates, relative to each other or to tooling for head suspension fabrication purposes.
A method for locating a component, including a component of a head suspension assembly, relative to a fixed datum is also provided. The method includes the steps of providing a component having a compliant feature and a datum engaging surface; providing a datum for engaging the datum engaging surface; providing a first pin for engaging the compliant feature; and manipulating the component with respect to the datum and first pin. The manipulation causes the first pin to engage and deflect the compliant feature when the datum engaging surface of the component is engaged and positioned with respect to the datum.